Lanthanum was discovered in 1839 by Swedish chemist Carl Gustav Mosander, when he
partially decomposed a sample of cerium nitrate by heating and treating the resulting salt
with dilute nitric acid. From the resulting solution, he isolated a new rare earth
he called lantana. Lanthanum was isolated in relatively pure form in 1923.

The word lanthanum comes from the Greek, lanthanein, "to lie
hidden". That is an apt description since lanthanum generally occurs along with
other so-called rare earth elements and is very difficult to separate. The
abundance of the metal is similar to that of zinc or nickel.

Lanthanum is a silvery white metallic element belonging to group 3 of the periodic
table and often considered to be one of the lanthanides. Found in some rare-earth
minerals, usually in combination with cerium and other rare earth elements.
Lanthanum is malleable, ductile, and soft enough to be cut with a knife. It is one
of the most reactive of the rare-earth metals. The metal reacts directly with
elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with
halogens. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum
slowly, while hot water attacks it much more rapidly.

1s2

2s2

2p6

3s2

3p6

3d10

4s2

4p6

4d10

5s2

5p6

5d1

6s2

For that reason the metal is usually stored under oil or kerosene. Most lanthanum is
extracted from monazite sands. Lanthanum is used in the electrodes for
high-intensity carbon-arc lamps and also in the production of high-purity europium metal
(element 63).

Lanthanum oxide and the boride are used in electronic vacuum tubes as hot cathode
materials with strong emissivity of electrons. Crystals of LaB6 are used
in high brightness, extended life, thermionic electron emission sources for scanning
electron microscopes.

in Gas tungsten arc welding electrodes, as a substitute for radioactive thorium.

Hydrogen spong alloys can contain lanthanum. These alloys are capable of storing up to
400 times their own volume of hydrogen gas in a reversible adsorption process.

Petroleum cracking catalysts.

Gas lantern mantles.

Glass and lapidary polishing compound.

La-Ba age dating of rocks and ores.

Lanthanum carbonate is used medically as a phosphate binder for the treatment of
hyperphosphatemia.

Lanthanum nitrate is mainly applied in specialty glass, water treatment and catalyst.

Cerium activated Lanthanum bromide is the recent inorganic scintillator which has a
combination of high light yield and the best energy resolution.

Like horseradish peroxidase, lanthanum is used as an electron-dense tracer in molecular
biology.

Lanthanum has no known biological role. The element is not absorbed orally, and
when injected its elimination is very slow. Lanthanum carbonate was approved as a
medication (Fosrenol®, Shire Pharmaceuticals) to absorb excess phosphate in cases of
end-stage renal failure. Some rare-earth chlorides, such as lanthanum chloride (LaCl3),
are known to have anticoagulant properties.

While Lanthanum has pharmacological effects on several receptors and ion channels its
specificity for the GABA receptor is unique among divalent cations. Lanthanum acts at the
same modulatory site on the GABAR as zinc- a known negative allosteric modulator. The
Lanthanum cation La3+ is a positive allosteric modulator at native and
recombinant GABA receptors, increasing open channel time and decreasing desensitization in
a subunit configuration dependent manner.

Naturally occurring lanthanum is composed of one stable (139La) and one
radioactive (138La) isotope, with the stable isotope, 139La,
being the most abundant (99.91% natural abundance. 38 radioisotopes have been
characterized with the most stable being 138La with a half-life of 105×109
years, and 137La with a half-life of 60,000 years. All of the remaining
radioactive isotopes have half-lives that are less than 24 hours and the majority of these
have half lives that are less than 1 minute. This element also has 3 meta states.

The isotopes of lanthanum range in atomic weight from 117 u (117La) to 155 u
(155La).

Lanthanum has a low to moderate level of toxicity, and should be handled
with care. In animals, the injection of lanthanum solutions produces glycaemia, low
blood pressure, degeneration of the spleen and hepatic alterations.

(Gr. lanthanein, to lie hidden) Mosander in 1839 extracted a new earth lanthana, from
impure cerium nitrate and recognized the new element. Lanthanum is found in rare-earth
minerals such as cerite, monazite, allanite, and bastnasite. Monazite and bastnasite are
principal ores in which lanthanum occurs in percentages up to 25 and 38% respectively.
Misch metal, used in making lighter flints, contains about 25% lanthanum. Lanthanum was
isolated in relatively pure form in 1923, iron exchange and solvent extraction techniques
have led to much easier isolation of the so-called "rare-earth" elements. The
availability of lanthanum and other rare earths has improved greatly in recent years. the
metal can be produced by reducing the anhydrous fluoride with calcium. Lanthanum is
silvery white, malleable, ductile, and soft enough to be cut with a knife. It is one of
the most reactive of the rare-earth metals. It oxidizes rapidly when exposed to air. Cold
water attacks lanthanum slowly, and hot water attacks it much more rapidly. the metal
reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus,
sulfur, and with halogens. At 310oC, lanthanum changes from a hexagonal to a
face-centered cubic structure, and at 865oC it again transforms into a
body-centered cubic structure. Natural lanthanum is a mixture of two stable isotopes,
138La and 139La. Twenty three other radioactive isotopes are recognized. Rare-earth
compounds containing lanthanum are extensively used in carbon lighting applications,
especially by the motion picture industry for studio lighting and projection. This
application consumes about 25% of the rare-earth compounds produced. La2O3
improves the alkali resistance of glass, and is used in making special optical glasses.
Small amounts of lanthanum, as an additive, can be used to produce nodular cast iron.
There is current interest in hydrogen sponge alloys containing lanthanum. These alloys
take up to 400 times their own volume of hydrogen gas, and the process is reversible. Heat
energy is released every time that they do so; therefore these alloys have possibilities
in energy conservation system. Lanthanum and its compounds have a low to moderate acute
toxicity rating; therefore, care should be taken in handling them. The metal costs about
$5/g.